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251.
Akiyoshi?ShinadaEmail author Syuhei?Ban Yuichiro?Yamada Tsutomu?Ikeda 《Journal of Oceanography》2005,61(4):645-654
The planktonic food web structure in the subarctic coastal water off Usujiri south-western Hokkaido, Japan was investigated from June 1997 to June 1999, based on seasonal biomass data of pico- (<2 µm), nano- (2–10 µm), micro- (10–200 µm) and mesoplankton (>200 µm), and path analysis using the structural equation model (SEM). In spring, microphytoplankton predominated due to diatom bloom, while pico- and nanophytoplankton predominated in the other seasons, except November and December 1997. The seasonal change in size distribution of heterotrophic plankton was almost similar to that of phytoplankton, and mesozooplankton biomass was high in spring. The path analyses suggest that the main channel in the microbial food web could vary according to phytoplankton size composition, indicating not only the classical food chain (microphytoplankton - copepods) but also the indirect route (microphytoplankton - naked dinoflagellates - copepods). 相似文献
252.
Akihide?KasaiEmail author Tateki?Fujiwara Takuma?Kimura Hirokatsu?Yamada 《Journal of Oceanography》2004,60(5):817-824
To clarify the time change in water exchanges between Ise Bay and the adjacent ocean, repeated hydrographic observations were
conducted along the longitudinal section in Ise Bay. The results show that the mixing condition at the bay mouth (Irago Strait)
changed fortnightly in summer. During the spring tides, the strait water below the pycnocline was well-mixed and nearly homogeneous.
By contrast, it was weakly stratified during the neap tide. There is a strong negative correlation between the tidal range
and the density difference between the upper and lower layers at the strait. In summer, the intrusion depth of oceanic water
into the bay and consequent hydrographic conditions inside the bay changed frequently according to the tidal strength. During
the spring tides a prominent bottom front was created at the bay mouth, indicating that the strait water, which is a mixture
of oceanic and bay waters, intruded through the middle layer. On the other hand, during the neaps, cold and saline oceanic
water intruded through the bottom layer into the bay. The intrusion depth is significantly correlated with the tidal range.
It is considered that the wellmixed strait water, which has a density equivalent to the middle layer inside the bay, is lighter
than the bottom bay water and thus intrudes through the middle layer during the spring tides, while insufficient mixing makes
the bottom water at the strait heavier than the bay water, leading to the bottom intrusion during the neap tides. 相似文献
253.
We have attempted to develop an expert system to evaluate the favorability of uranium exploration projects using the Data-directed Numerical Method (DdM). We developed the system for the Macintosh personal computer, so as to facilitate the iterative processes of trial and error inherent in the DdM. In a detailed case study, we use the above system to evaluate the favorability of the Alligator Rivers Uranium Field, Northern Territory, Australia. The favorability of the target area is evaluated by considering several exploration parameters related to the geological factors controlling ore formation. The selection of appropriate exploration parameters is important to the success of the method. We then selected 15 model cells to validate each exploration parameter and also to design the exploration model by the application of the chi-square test. The result of the favorability evaluation, as displayed by the developed system, indicates that our designed exploration model is acceptable. By employing the above processes we conclude that the system using the DdM is applicable as an exploration tool and is useful in establishing an exploration model. 相似文献
254.
Masaaki Okuda Hiroomi Nakazato Norio Miyoshi Takeshi Nakagawa Hiroko Okazaki Saneatsu Saito Asahiko Taira 《Island Arc》2006,15(3):338-354
Abstract The 250-m Choshi core (CHOSHI-1), drilled from hemipelagic muds of the Inubo Group, has been physically, geochemically and tephrochronologically analyzed back to 1 Ma. We provide pollen results for the 19–169 m section of the core (400–780 ka) bracketed by the marker tephra Ty1 (equivalent to J4) and the Brunhes–Matuyama paleomagnetic boundary. The results show good agreement with the corresponding oxygen isotope (δ18 O) profile, with high δ18 O intervals dominated by boreal conifers Picea , Abies , Pinus (subgen. Haploxylon ) and Tsuga ( diversifolia ), whereas low δ18 O intervals are dominated by temperate conifers Cryptomeria , Taxaceae-Cephalotaxaceae-Cupressaceae and Sciadopitys . In order to confirm pollen-climate relations for the relevant taxa, a modern surface pollen dataset for the Japanese archipelago was consulted. In this analysis, the ratios of Cryptomeria / Picea and temperate/boreal conifers serve as proxies for the 100-kyr glacial/interglacial cycle during the Middle Pleistocene. Distinct signals for marine isotope stages (MIS) 11, 12, 13–15, 16, 17 and 18–19 are recognized in accordance with the tephrochronology and δ18 O of the same core. Application of the criteria to an independent pollen record from Lake Biwa provides an integrated pollen stratigraphy for mid-latitude Japan during the past 800 ky. Some degree of uncertainty remains in the chronology of the MIS13–15 interval, relating to the uncertainty in the eruption age of widespread tephra Ks11. 相似文献
255.
A wind tunnel was constructed to study mountain lee-wave phenomena and heated-island effects. The present wind tunnel appears to have several advantages over a towing tank facility for modeling atmospheric gravity-wave phenomena, i.e., non-uniform approach flows, stationary measuring conditions, variation of boundary temperature condition in the longitudinal direction, and no slip at the wall. Simple design criteria and characteristics of the present wind tunnel are discussed. A numerical program was utilized to explain peculiar standing-wave disturbances in the wind-tunnel test section. The above disturbances seemed unavoidable under the chosen mechanical constants. Nevertheless, a practical solution was found by extending the tunnel length.Postdoctoral Fellow, Princeton University, New Jersey, U.S.A.Associate Professor, Fluid Mechanics Program, Colorado State University, Fort Collins, U.S.A. 相似文献
256.
An Active Mass Driver (AMD) system is proposed to suppress actively the response of a building to irregular external excitations such as earthquakes and typhoons. This system has been introduced to an actual ten-storey office building for the first time in the world. The system controls the motions of a structure by means of an external energy supply. It consists of an auxiliary mass installed in a building and an actuator that operates the mass and produces a control force which counters disturbances to the building. The design method of the AMD system, including the location of the installation and the capacity and stability of the system, is proposed. Simplification of the control algorithm is also described. 相似文献
257.
Masaaki Murano 《Journal of Oceanography》1970,26(3):137-150
A list of the 21 species represented in the collection by the bottom-net is given. Of these, 5 are impossible to be identified
with the already known species, especially 2 are reserved as their genera are undecided. It is found that there are 2 races
inHolmesiella affinis
Ii, the large-sized and the small-sized, as like as the most related species,H. anomala
Ortmann. As to a species,Pteromysis amemiyai
Ii, the development of the marsupium is discussed on the basis of an adult female collected by the ORI-net. The occurrence of
2 species,Petalophthalmus oculatus
Illig andPseudomma calloplura
Holt andTattersall, is a new record in the Pacific. For the former species, moreover, an ecological property of the habitat is discussed. 相似文献
258.
Kazuya Ono Kay I. Ohshima Tokihiro Kono Motoyo Itoh Katsuro Katsumata Yuri N. Volkov Masaaki Wakatsuchi 《Journal of Oceanography》2007,63(2):281-291
Intensive CTD observations that resolve the mean and tidal components were done with a total of 129 casts in summer of 2001
at Bussol’ Strait. Based on these data and all the available historical data, we have revealed the outflow from Bussol’ Strait
to the Pacific and the significant diapycnal mixing in the strait. In the range 27.0−27.3σ
θ
, the water property in Bussol’ Strait is almost identical to that of the Kuril Basin Water (KBW). The KBW out of Bussol’
Strait forms a water mass front with the East Kamchatka Current Water (EKCW). This front also corresponds to the front of
the Oyashio Current. In the lower part of the intermediate layer (27.3−27.6σ
θ
), part of the water in the strait is characterized by lower temperature, lower salinity, and higher dissolved oxygen than
that of KBW and EKCW, which can be explained only by the diapycnal mixing. The strong diapycnal mixing in the strait can also
be shown by the density inversion, occurrence frequency of which corresponds well to the amplitude distribution of the diurnal
current. In the density range 26.7−26.8σ
θ
, the water in Bussol’ Strait has the lowest potential vorticity, suggesting that it is a source region of the low potential
vorticity water. Seasonal change of the water can reach up to a density of 26.8σ
θ
around Bussol’ Strait. This leads us to propose that the combination of winter convection and local tidal mixing leads to
effective ventilation of the intermediate layer. 相似文献
259.
Uranium in coastal sediments of Tokyo Bay and Funka Bay 总被引:2,自引:0,他引:2
Shizuo Tsunogai Seiya Nagao Shintaro Watanabe Yoshiaki Takahashi Kazunari Suzuki Masatoshi Yamada Koh Harada 《Journal of Oceanography》1990,46(5):211-218
The sediment cores from Tokyo Bay and Funka Bay were analyzed for U and its isotopic ratio,234U/238U, after dissolving them in 0.1 M HCl, and 30% H2O2 in 0.05 M HCl. A small fraction of U in the anoxic sediments was dissolved in 0.1M HCl and even the added yield tracer,232U, was lost. The isotopic ratio of H2O2 soluble U in the sediments was equal to that of seawater, suggesting that the H2O2 soluble U in the sediments is authigenic. The 6M HCl solution dissolved part of the lithogenic U besides the authigenic U. The depth profiles of U from the two bays resembled each other. The authigenic U comprised more than half of the total U even at the surface and increased with depth down to 70 cm, showing small maxima at about 20 cm. The concentration of refractory U was nearly constant with depth and similar to that of the pelagic sediments. The highest U concentration, 6 µg g–1 which was about 5 times that of the pelagic sediments, was observed in the layer between 70 and 160 cm depth in Tokyo Bay. The annual sedimentation rates of U in the Tokyo Bay sediments were 2.6 tons at the surface and 7.0 tons at the 70–160 cm depth. The increase in U with depth should be due to the deposition of interstitial U either diffusing downward from the surface indicating the trapping of seawater U, or otherwise diffusing upward from the deeper layer indicating the internal cycling of U within the sediments. 相似文献
260.
Hiroyuki Yamada Futoshi Nakamura Yasuharu Watanabe Marie Murakami Takeshi Nogami 《水文研究》2005,19(13):2507-2524
Permeability of a streambed is an important factor regulating nutrient and oxygen availability for aquatic biota. In order to investigate the relationship, an accurate permeability should be measured. However, it is difficult to measure permeability in a coarse gravel bed using a conventional permeability test. Moreover, turbulent flow may occur in coarse bed material, and then deviations from Darcy's law do occur. Thus, permeability calculated following Darcy's law may be overestimated under turbulent flow conditions and should be corrected. The packer test can be used in highly permeable gravel beds. We developed a field method applicable to a gravel bed using the packer test and derived an equation adopting a law of turbulent flow to study the problems under any type of flow condition. The accuracy of the equation was examined using a laboratory flume with a gravel bed. The results suggested that permeability calculated from Hvorslev's equation is overestimated for turbulent flow. In contrast, our equation, developed here, could evaluate permeability accurately under any type of flow condition. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献